1. Field of the Invention
The present invention relates to display manufacturing field, more particular to a manufacturing method of a mask plate and an array substrate.
2. Description of Related Art
The display panel for manufacturing the display includes the LCD (Liquid Crystal Display) panel and the OLED (Organic Light-Emitting Diode) panel. They are all required the photolithography process to formed the circuit.
The photolithography process mainly includes photoresist four steps of photoresist coating, exposure, development and etching. After forming a metal layer on a glass substrate, it start to coat the photoresist, and a photoresist layer is formed on the metal layer; then, exposing the photoresist layer; after developing the exposed photoresist layer, the photoresist layer forms a pre-designed circuit pattern; finally, etching the metal layer, wherein, the metal without the protection of the photoresist is etched away, and the remaining metal forms the circuit.
It is well known that the display panel includes the effective display area (AA, Active Area) and the non-effective display area surrounded the effective display area. In the effective display area, it includes various signal lines such as the scanning lines and the data lines. The non-effective area includes fanout leads, wherein, one end of each fanout lead connects to the signal line, and the other end of each fanout lead connects to peripheral driver chip. With reference to FIG. 1, which is schematic view illustrating a display panel of the prior art, and it also enlarges the fanout leads. Because the fanout leads connected to the signal lines correspondingly, when they transmit signals, the fanout leads function as the load of the signals. If the fanout leads are all straight lines, the effective lengths of the outer periphery fanout leads are greater than the effective lengths of the middle portion of the fanout leads such that the resistances of the outer periphery fanout leads are greater than the resistances of the middle portion of the fanout leads. Therefore, the different signal lines will have different loads so as to impact the signal transmission, which results in image display unevenness of the display. This phenomenon is called the display unevenness (Fallout Mura) phenomenon. To overcome this problem, the middle portions of the fanout leads are curved to increase the effective lengths of the middle portion of the fanout leads, which could reduce the difference in resistances with the outer periphery fanout leads.
However, when using the photolithography process of the prior art, due to the limited capacity of the process, the curve portion of the fanout lead is often difficult to achieve pre-designed line width, which results in further increasing the difference in resistances. With, reference to FIG. 2, which is a comparison drawing of a fanout lead on the display panel formed before and after by the conventional art. Part (a) of FIG. 2 shows a desired shape of a curve portion of the fanout lead before forming. The line width of the curve portion is equal to the line width of the other portion. Part (b) of FIG. 2 shows an actual shape of the curve portion of the fanout lead after the formation available by the current photolithography process. The line width of the curve portion is greater than the line width of the other portion.
The reasons for this result are: In the exposure step, the light path is difficult to achieve perfectly collimated, there is a small amount of lateral light. The exposure area will be irradiated by collimated light and the lateral light at the same time. For the part (b) of FIG. 2, the A area of the fanout lead is not irradiated by the light, the A area is surrounded by three sides, that is, the A area is not exposed by the lateral light at the three sides, but the other area can he irradiated with the collimated light and lateral light. Therefore, the photosensitive intensity of the A area is weaker than other exposed areas, and the chemical reaction of the photoresist is slower such that when developing and etching in the subsequent steps, the developing rate and the etching rate of the A area is slower than other exposed areas. Finally, the curve portion of the fanout lead adds the A area so that the line width of the curve portion of the fanout lead is increased, and the resistance is correspondingly smaller such that the difference in resistances becomes larger.